Hi Steve,
These are still available as a brand new item, and manufactured (in Holland) to the same specification as they were.
They come with 3 period stickers, Including the classic sticker, as shown. Not cheap, once you pay freight, land them & GST
I needed these as they are correct for the Rally Sprint

https://konimarket.com/products/1968...shock-rear-573

Or your specialist GM aftermarket supplier may have them